Method and machine for form rolling



April 1968 H. w. BROWN, SR 3,379,042

METHOD AND MACHINE FOR FORM ROLLING Filed Dec. 27, 1965 5 Sheets-Sheet lillil; INVEA/ TOR.

1i 5 HARRY 14/. BROWN'S/2 F76. 2 BY P 1963 H. w. BROWN, SR 3,379,042

METHOD AND MACHINE FOR FORM ROLLING Filed Dec. 27, 1965 5 Sheets-Sheet 2April was H. w. BROWN, SR 3,379,042

METHOD AND MACHINE FOR FORM ROLLING Filed Dec. 27, 1965 5 Sheets-Sheet YFIG /2 //V VE N TOR HA RR Y W. BROWN, 57?.

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METHOD AND MACHINE FOR FORM ROLLING Filed Dec. 27, 1965 5 Sheets-Sheet 45 Sheets-Sheet 5 H. W. BROWN, SR

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United States Patent 3,379,042 METHOD AND MACHINE 180R FORM RQLLHNGHarry W. Brown, Sn, Euclid, Ohio, assignor to The National Acme Company,a corporation of (lhio Filed Dec. 27, 1965, Ser. No. 516,348 18 Claims.(Cl. 72-10) The invention relates in general to the method and a machinefor rolling a form on a workpiece and more par ticularly to a method anda machine for rolling a form such as a deep thread or an annular orhelical fin on the exterior surface of a tube.

Tube finning machines have been made in the past to create a fin on atube, for example, for heat exchangers to increase the effective surfacearea on the exterior of the tube. This is an example of one form ofthread rolling or roll forming wherein the material of the workpiece isconsiderably extruded or cold formed by a considerable displacement ofthe metal or material of the workpiece. Other examples could includerolling square threads or deep threads on a workpiece. In such cases therolls which engage the exterior surface of the tube are underconsiderable radial pressure. To cause the appreciable cold flow of theworkpiece where a deep helical fin is desired on the workpiece or tube,the forming rolls must be machined to a complementary shape and thuswill also have a long thin fin. In the past considerable difiiculty hasbeen found in machining such form rolls and one solution has been to usestacked discs, each with sharpenededgcs, as the forming roll. Howeverregardless of how the forming roll is constructed, whether in one pieceor in several stacked discs, the long narrow tapering edge on thecomposite roll has been subject to considerable breakage. This breakagehas been considered a necessary evil where such a deep fin was desiredand this was one reason for using the stacked discs so as to aidreplacement of a disc which had broken. However, even this causedconsiderable down-time of the machine while the rolls were beingrepaired or replaced.

The breakage of the prior art forming rolls has now been discovered tobe caused by the subjecting of the rolls to other than purely radialforces. For example, a longitudinal force on the roll relative to thetube or workpiece can easily break off the edge of the long tapering finon the roll. Also a rotational force on the roll relative to the rollhead or relative to the tube can in turn cause a longitudinal forcewhich again will break the fin on the form roll. Still further it hasbeen found with deep penetration of form rolls into the exterior surfaceof a tube to cold form a deep fin on the tube, that an internal mandrelwas necessary to prevent collapse of the tube. In the prior art thismandrel was in many cases stationary and with a longitudinally movingtube this created considerable friction again introducing a longitudinalstrain on the form rolls to break off the fin. Further this longitudinalfriction developed considerable heat and the heat further elongated thetube thus making it dilficult to establish a controlled length of thetube and the pitch or lead of the helical fin. The deep penetration andcold flow of the metal also resulted in considerable elongation of thetube in the exit and of the forming rolls. The longitudinal elongationfrequently tended to move the mandrel in a forward direction and wherethe mandrel was held against this movement this caused longitudinalforces tending to break the fins on the forming rolls.

Accordingly, an object of the present invention is to obviate theabove-mentioned disadvantages.

Another object of the invention is to provide a form rolling machine toroll deep threads, fins or forms on a workpiece or tube without anylongitudinal forces on the forming rolls to substantially eliminatebreakage of these forming rolls.

Another object of the invention is to provide servomotor poweredmovement of the relative longitudinal movement of the roll head andworkpiece to eliminate longitudinal forces on the forming rolls.

Another object of the invention is to provide a machine wherein acontrolled feed rate of relative movement of the tube and roll head isprovided in order to establish movement for unformed land portions onthe tube yet with this motor acting as a servomotor under control of aservovalve or control element for the form rolling of the tube. Furthera follow-up movement is provided between the servovalve and the housingthereof in accordance with the movement of the motor.

Another object of the invention is to provide a means whereby a mandrelmay be moved longitudinally within the tube to be exterioriy formed andto maintain the mandrel in position to prevent collapse of the tubedespite the fact that the mandrel is frictionally urged in one directionby the action of the form rolling.

The invention may be incorporated in a form rolling machine, comprising,in combination, a frame, a carriage movable longitudinally on saidframe, a motor connected to drive said carriage longitudinally of saidframe, a form roll head including a plurality of form rolling rollsthereon, means to relatively longitudinally move said roll head and atube to be form rolled in accordance with longitudinal movement of saidcarriage, means to establish a controlled feed rate of said motor for aforward longitudinal movement of the carriage, means to relativelyrotate said roll head and the tube to roll a form on the exteriorsurface of the tube, a control element and housing, the relativerotation of said roll head and tube while in engagement relativelylongitudinally moving the tube and the head, means to relatively movesaid control element and housing in accordance with the relativelongitudinal movement of said roll head and the tube, means connectingsaid control element and housing to said motor for control of same toestablish forward movement of said carriage, and means connecting saidcontrol element and housing for relative followup movement in accordancewith longitudinal movement of said carriage.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims, taken in conjunctionwith accompanying drawings, in which:

FIGURE 1 is a longitudinal sectional view through a form rolling headwhich may be used in the invention;

FIGURE 2 is an end view of the form rolling head;

FIGURE 3 is an enlarged view of a forming roll and the tube beingformed;

FIGURE 4 is a view of the completed workpiece of tube with the helicalfin thereon;

FIGURES 5 through 16 are plan views, diagrammatical in many details,illustrating the sequence of operation for rolling a fin on a tube;

FIGURE 17 is a longitudinal elevational view, partly in section of thecarriage portion of the machine of FIG- URE 5; and

FIGURE 18 is an end view of the carriage portion of the machine shown inFIGURE 17.

The form rolling method may be performed by a machine 20 illustrated asrolling a helical form on the exterior surface of a workpiece. Themachine 20 is illustrated as rolling a deep helical fin on a workpieceor tube 21. This tube 21 is illustrated in FIGURE 4 and showing thehelical fin 22. The machine 20 includes a frame 25 having a first end atthe right and a second end at the left. A carriage 26 is disposedgenerally at the right end of the frame 25 and is slidably journalledfor longitudinal movement on a way 27. The carriage 26 has mountedthereon a motor 29 shown as a hydraulic rotary motor. This motor 29drives a pinion 3t engaging rack 31 fixed on the rear of the frame 25.Accordingly rotation of the pinion 30 moves the carriage 26longitudinally of the frame 25. A servovalve 33 has a housing 34containing a servovalve spool 35. This valve spool may be considered acontrol element. The servovalve housing 34 is fixed on the carriage 26and has fluid conduits interconnecting with the hydraulic motor 29, asdiagrammatically illustrated in FIGURE 10.

The machine also includes a plurality of rollers 37 mounted oncantilever arms 28 from the frame so as to avoid interference with thecarriage 26. These rollers 37 support the tube 21 to be form rolledalong the longitudinal axis 39 of the machine 20.

Mounted in a central area of the frame 25 is a support 40 for a formrolling head 41. The support 40 journals the roll head 41 for rotationaround the longitudinal axis 39 and this head is better shown in FIGURESl and 2. The head 41 is adapted to be rotated around the axis 39 by anysuitable means such as the motor 42. This motor 42 may rotate at aconstant speed to establish a constant rate of forming the fin 22 on thetube 21.

FIGURES l and 2 better show the construction of the form rolling head 41as including a rotatable housing 45 rotatable by the motor 42. Blocks 46carry axles 47 on each of which a forming roll 48 is freely journalled.Four such forming rolls may be used and in FIGURE 2 only two such rollsare illustrated in order to show other parts of the mechanism. Eachblock 46 is slidable radially in the housing 45 and is urged outwardlyby a spring 49 and by work pressure. Each forming roll 48 cooperateswith the others to roll a helical fin or thread on the tube 21. In orderto accomplish this the axis of the axles 47 may be parallel to thelongitudinal axis 39, together with having a helical form on the formingrolls 48. Alternatively, a helical form on the rolls together with axesof the rolls skewed an amount corresponding to the helix will roll anannular groove on the workpiece and also longitudinally move theworkpiece relative to the roll head. Alternatively as illustrated inthis case, the forming rolls 48 may be provided with annular groovesthereon and may be simply constructed by a plurality of stacked discs50. Where annular grooves are used on the forming rolls 48, then theaxes of the axles 47 are skewed an appropriate amount corresponding tothe helix desired to be formed on the workpiece.

A cup 52 surrounds the rotatable housing 45 and has a plurality ofrollers 53, each one to engage a different block 46. Each block has acam surface 54 so that upon longitudinal retraction of the cup 52 thesprings 49 and the work rolling pressure will move the blocks 46 outwardly to open the head. In this condition the forming rolls 48 will notengage the tube 21. When the cup 52 is moved forwardly to the positionshown in FIGURE 1 the rollers 53 move the blocks 46 inwardly to theclosed position of the head. This closed position establishes therollers for full depth penetration of the form of these rolls into thetube 21. A spool 55 is fastened to the rear of the cup 52. A yoke 56engages this spool 55. Power means such as a fluid motor 57 is connectedto actuate the yoke 56 to open and close the head 41. The fluid motor 57is controlled by suitable means, shown diagrammatically in FIGURE 1 Amandrel 60 is diagrammatically shown in the FIG- URES 516. This mandrelhas the left end thereof carried in a mandrel support 61. This support61 may move longitudinally of the frame 25. A motive means 62, shown asa fluid cylinder in FIGURE 6 has a piston 64 connected by means of acable 63 to the mandrel support 61. Movement of the piston 64 within themotive means cylinder 62 will move the mandrel support 61 longitudinallyof the fram6e 25, between the positions shown in FIGURES 5 and A tubelength sensing device 66 includes a support 67 longitudinally slidableon the frame 25. The device 66 further includes a tubular part 68extending toward the roll head support 40. The free end 69 of thetubular part 68 is adapted to engage the forward end or second end 72 ofthe tube 21, as illustrated in FIGURE 7 compared to FIGURE 6. The firstend 71 of the tube 21 is adapted to be clamped in a fixture 73 on thecarriage 26, see FIGURES 5 and 17. The tubular part 68 thus surroundsthe mandrel 60 and is of a diameter to engage the second end 72 of thetube 21. Adjustable pilot valves 74 are carried on the frame 25 andengaged by a cam 75 carried on the tube length sensing support 67. Thesevalves 74 may be also limit switches, for example, and are connected tocontrol the opening and closing of the roll head 41 by connection means72 as diagrammatically illustrated in FIGURES 7 and 10. The roll head 41is diagrammatically illustrated in FIGURES 5-16 in order to simplifythese figures. For example, these valves may be limit switches tocontrol energization of solenoids moving a fluid valve for selectivecontrol of fluid to the fluid motor power means 57, shown in FIGURE 1.Briefly when the cam 75 is in engagement with one of the limit switchesor valves 74, as shown in FIGURES 5, 6, and 7, then the roll head isopen. When the cam 75 is not in engagement with one of the valves orswitches 74, for example as shown in FIGURE 8, then the roll head 41 isclosed.

FIGURE 17 illustrates the carriage 26. The clamping fixture 73 may beclamped by a screw 78 to clamp the first end or right end 71 of the tube21 to a plate 79. This plate is journalled for longitudinal slidingmovements on a rod 80 fixed on the carriage 26. Linear bearings 81 maybe provided for low fricton free floating movement of the plate 79,within limits. The plate 79 fixedly carries a bracket 82 into which amicrometer adjustment 83 is screwed and which is in alignment with thevalve spool 35. A tension spring 84 urges the plate 79 to the right asviewed in FIGURE 17 and an internal spring 85 in the servovalve housing34 urges the valve spool 35 to the left, see FIGURE 10.

FIGURE 10 illustrates diagrammatically the hydraulic circuit used forcontrol of the fluid motor 29. This motor controls movement of thecarriage 26 and accordingly the relative longitudinal movement of thetube 21 and roll head 41.

A pump 87 is illustrated in FIGURE 10 as a source of fluid pressure. Adirectional valve 88 is illustrated as a four-way valve with a neutralposition. This valve 88 may be controlled by forward and reverse controldevices 89 and 90. These may be solenoids, for example. These forwardand reverse control devices 89 and 90 are connected by means 91 forcontrol by a handle 92 which may be mounted for convenient use on themachine 20. In FIG- URE 10 this handle 92 is shown in the forwardposition and thus the valve 88 is shown in the forward position whereinfluid pressure is directed into a conduit 93 and a conduit 94 isconnected to drain 95. Pressure in conduit 93 causes the fluid motor 29to rotate in a forward direction causing forward movement of thecarriage 26. This moves the tube forwardly, that is from the first endtoward the second end thereof, and toward the roll head 41. A checkvalve 97 in the conduit 94 diverts fluid flow through the servovalve 33for this forward movement. The servovalve 33 has been diagrammaticallyillustrated in FIG- URE 10 as being a restrictor valve variablyrestricting the flow of fluid therethrough. Flow is also through anothercheck valve 98 and a branch conduit 99. Mechanical means shown as themicrometer adjustment 83 acts on the servovalve 33 to partially biasopen this servovalve 33. This establishes a controlled feed rate offorward movement of the carriage 26. Viewing FIGURES 10 and 17, thespring 85 pushes the valve spool 35 to the left tending to open thisvalve. This tendency to open the valve is resisted by the tension spring84. The micrometer adjustment 83 may thus be changed to vary thecontrolled feed rate of the carriage 26.

OPERATION A tube 21 to be roll formed may have the first end 71 thereofclamped in the clamping fixture 73 as illustrated in FIGURES 5 and 17.This tube 21 will be supported on the rollers 37 concentric with thelongitudinal axis 39 of the machine 20. A valve 101 supplied by pressurefluid from a pump 102 may next be moved to move the piston 64 to theleft to move the mandrel support 61 to the right. This moves the mandrel60 inside the full length of the tube 21. The rear end or first end ofthis mandrel 60 may thus engage a stop 103 on the clamping fixture '73on the carriage 26. This movement of the mandrel support 61 also movesthe tube length sensing device 66 to the right near the roll head 41.This will be as shown in FIGURE 6. The motor 42 may then be actuated torotate the roll head 41, for example, at a predetermined constant rate.The handle 92 may then be moved to the forward position as illustratedin FIGURE 7. This actuates the hydraulic system to move the valve 88 tothe forward position, as shown in FIGURE 10. Pump pressure throughconduit 93 actuates the fluid motor 29 in the forward direction. Thismotor 29 drives the carriage 26 to the left, or in the forwarddirection. The rate of movement will be at a controlled feed ratedependent upon the micrometer adjustment 83 which controls the openingof the servovalve 33. This could also be effected by a separate valve inparallel with the servovalve 33 but for simplicity, the two functionsmay be combined in the servovalve 33. This will move the tube 21 to theleft, with the forward end 72 thereof engaging the free end 69 of thetube length sensing device 66, at the point shown in FIGURE 7.

The controlled feed rate of the motor 29 and carriage will continue tomove the tube to the left from the position shown in FIGURE 7,overcoming the lesser force of the fluid motor motive means 62, whichmay be an air cylinder. When the cam 75 rides off the first limit switch74, then the roll head 41 will close to begin to form a helical threador fin on the tube 21. This will be as viewed in FIGURE 8 and there maybe an unfinned land 105 at the forward end of the tube 21. This wouldhelp utilization of the tube 21 in a heat exchanger or other endproduct.

The closing of the rotating head 41 on the non-rotating tube 21 willcause a longitudinal movement of the tube through the roll head 41. Thisis because of the threading action of the fin formed on the tube and thelongitudinal component of the lead or pitch of the helical thread or finon the roll or on the workpiece. This component will establishlongitudinal movement of the tube because of the rotation of the head 41but at a different rate from the conrolled feed rate. Preferably therate of pulling the tube through the head is at a faster rate than thecontrolled feed rate. Accordingly the tube 21 pulls on the clampingfixture 73. This in turn moves the plate 79 forwardly, see FIGURE 17 andthe internal spring 85 moves the valve spool 35 forwardly to increasethe fluid flow and increase the rate of movement of the fluid motor 29.This increases the rate of the carriage 26 to a second rate so that thefluid motor 29 acts as a servomotor under control of the servovalve 33.The carriage 26 is accordingly moved at the same rate of speed as thetube 21 in its passage though the roll head 41. The fact that theservovalve housing 34 is fixed on the carriage 26 is a means connectingthe con trol element 35 and housing 34 for relative follow-up movementin accordance with the longitudinal movement of the carriage. Thislongitudinal movement of the carriage is that which provides relativelongitudinal movement between the tube 21 and roll head 41. The motor 42rotating the head 41 is that which provides relative rotational movementbetween the head 41 and tube 21 and thus establishes the rate ofrelative longitudinal movement between the tube 21 and head 41.

FIGURE 9 illustrates a position of further progress of the tube 21through the head 41. The cam 75 has engaged a second one of the limitswitches 74 to open the roll head 41. FIGURES l0 and 11 show that thiscam has remained in engagement with the limit switch 74 for a lengthsuflicicntly to establish an unthreaded or unfinned land 1106 on thetube 21. Such an unfinned land 106 may be used to provide a smoothexterior land portion on the tube 21 for support of the tube whenassembled in the end product such as a heat exchanger. FIGURE 12 againshows the roll head 41 opened by the cam engaging another limit switch74. FIGURE 13' shows this cam 75 about to ride of? this limit swich 74and thus another land 106 will be formed as shown in FIGURES l3 and 14.

The form rolling action on the tube 21 elongates the finned portion ofthe tube 21. This is because of the considerable extrusion or cold flowof the metal or material forming the tube in order to form the very deepfins 22. For example, this tube may be A" in outside diameter and about.050" wall thickness. The complete helical fin 22 may be in the order of.080" deep with a remaining tube wall thickness 108 of about .020" to.030". This shows that the machine of the invention will produce a finof considerably greater radial depth than the remaining radial thicknessof the tube wall. This is a considerable deformation of the material ofthe tube wall. This cold flow of the material has been found to elongatethe finned section of the tube 21 about 25 percent. This elongationtakes place principally at the exit end of the forming rolls 48, whichis at the bottom of FIGURE 3. The mandrel 60 fits the inner diameter ofthe tube 21 with only a slight clearance 109. As the rolls 48 actradially inwardly on the tube 21, the inner tube wall 110 is supportedby the mandrel 60 to prevent collapse of this tube 21. As the finnedtube exits from the forming rolls 48 there is a slight amount ofresilient spring back of the tube 21 to provide a small clearance 111between the mandrel 60 and the tube 21.

FIGURE 8 illustrates the fact that the mandrel 60, even thoughresiliently urged to the right by the motive means 62, has beenfrictionally moved to the left by the action of the roll head 41elongating the tube. The longitudinal elongation of the tube 21 has beentoward the finned end of the tube 21. This frictionally moves themandrel 60 in the same direction and therefore the rearward end of thismandrel 60 has moved away from the stop 103 on the carriage 26. This isillustrated in FIG- URE 8. When the roll head 41 opens, as illustratedin FIGURE 9, or when the radial inward pressure of the rolls 48 on thetube 21, and hence the tube 21 on the mandrel 60 is slightly relieved,then the motive means 62 moves the mandrel 60 back to the right intoengagement with the stop 103. This is as illustrated in FIGURE 9. Themandrel is moved away from the stop 103 during each of the form rollingactions as illustrated in FIG- URES 8, l1, and 14. Each time that thehead 41 is opened, the mandrel 60 moves back to the right as illustratedin FIGURES 9, 12, and 15.

The fact that the motive means 62 is resilient in its urging toward theright in FIGURES 5l6, permits the mandrel 60 to be moved forwardly withthe elongation of the finned portion of the tube. This avoids thelongitudinal sliding friction between the mandrel and the tube whichotherwise would occur if the mandrel was held stationary. This was adifficulty in prior fin rolling machines and such longitudinal slidingfriction created considerable heat which further aggravated the strainon the finning or forming rolls. The present machine eliminates thissource of friction and such longitudinal strain on the rolls.Accordingly there is no longitudinal force on the fins or the firmingrolls relative to the tube and accordingly breaking of these rolls isgreatly reduced. Also with the elimination of the heat of friction thetube is not elongated for this reason, and accordingly exact length offinned sections may be established. This establishes an exact number offins per inch of tube length which is necessary to meet specificationsfor these finned tubes. In prior art machines which had a non-rotatinghead and gear driven rolls to rotate the rolls and the workpiece,

the elongation of the tube during the rolling action destroyed thepreciseness of the number of rolled fins per inch of length. Also insuch prior machines the threading action of the rolls onto the tube wasthat which longitudinally fed the tube through the head. This was aconsiderable longitudinal force applied on the slender fins of theforming rolls and this caused considerable breakage of these rolls. Inthe present machine, the motor 29, acting as a servomotor, supplies allof the force for the longitudinal movement of the tube to eliminate such10ngitudinal forces on the slender fins of the forming rolls.

FIGURE 16 illustrates the return to the left of the mandrel support 61,caused by reversal of the valve 101. Also the handle 92 is now moved tothe right to the reverse position, and this moves valve 88 to the right.This establishes full fluid flow into conduit 94 and the fiuid motor 29runs freely in the reverse direction. This returns the carriage 26 tothe right to the position shown in FIG- URE 16. The clamping fixture 73may now be released and the completed finned tube may be removed fromthe machine 20. The machine is now ready for another cycle of operation.

The present disclosure includes that contained in the appended claims,as well as that of the foregoing description. Although this inventionhas been described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts and steps may be resorted to without departing fromthe spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A form rolling machine, comprising in combination,

a frame,

a carriage movable longitudinally on said frame,

a motor connected to drive said carriage longitudinally of said frame,

a form roll head including a plurality of form rolling rolls thereon,

means to relatively longitudinally move said roll head and a tube to beform rolled in accordance with longitudinal movement of said carriage,

means to establish a controlled feed rate of said motor for a forwardlongitudinal movement of the carriage, means to relatively rotate saidroll head and the tube to roll a form on the exterior surface of thetube,

a control element and housing,

the relative rotation of said roll head and tube while in engagementrelatively longitudinally moving the tube and the head,

means to relatively move said control element and housing in accordancewith relative longitudinal movement of said roll head and the tube,

means connecting said control element and housing to said motor forcontrol of same to establish forward movement of said carriage, and

means connecting said control element and housing for relative followupmovement in accordance with longitudinal movement of said carriage.

2. A machine as defined in claim 1 including,

means to journal said form rolling rolls on said head for free rotationthereon.

3. A machine as defined in claim 1 including,

means to longitudinally move the tube by one end from the carriage andcommencing the form rolling operation on the other end of the tube.

4. A machine as defined in claim 1 including,

means to rotate the roll head and to hold the tube rotatively stationaryto have the form rolls rotate in engagement with the tube.

5. A machine as defined in claim 1 wherein said controlled feed rate isat a different rate of movement than that longitudinal movementestablished by the relative rotation of the roll head and tube while inengagement,

and said control of said motor by said control element and housingrelieving the form rolls from any axial force relative to the roll head.

6. A machine as defined in claim 1 including,

a hydraulic servomotor as said carriage motor,

a servovalve having a valve spool in a housing as said control elementand housing,

means to mount said servovalve housing on the carriage,

and means to control movement of said servovalve spool in accordancewith movement of the tube relative to said carriage.

7. A machine as defined in claim 1, including,

a mandrel,

motive means to relatively move said mandrel longitudinally inside thetube to prevent collapse of the tube during rolling of the form thereon,

the tube elongating during the form rolling action and frictionallyurging said mandrel to move longitudinally relative to one end of thetube,

said roll head being openable at least partially to relieve inwardpressure between the tube and said mandrel,

and said motive means returning said mandrel into position inside theportion of the tube within the roll head during the period of relief ofsaid inward pressure.

8. A machine as defined in claim 1, including,

said roll head being openable and being closable to engage a tube forrolling a form thereon,

means to open said roll head to establish an unformed land on the tube,

and said controlled feed rate of said motor continuing the forwardmovement of said carriage to produce said unformed land.

9. A machine as defined in claim 8, including,

a mandrel,

motive means to relatively move said mandrel longitudinally inside thetube to prevent collapse of the tube during rolling of the form thereon,

the tube elongating during the form rolling action and frictionallyurging said mandrel to move longitudinally relative to one end of thetube,

and said motive means returning said mandrel into position inside theportion of the tube within the roll head during the period ofestablishing said unformed land.

10. A machine to roll a deep thread on a tube having first and secondends comprising, in combination,

means to non-relatively hold the first end of the tube,

means to move said tube longitudinally from said first end toward saidsecond end,

a thread rolling head having thread forming rolls freely rotatablyjournalled in said head,

means to open said head to have the rolls spaced sufficiently to notcontact the tube and means to close the head to have the rolls form adeep thread in the tube,

power means to longitudinally forwardly move the tube toward the secondend,

means to close the head and to rotate the head to roll a helical threadon the exterior of the tube,

the thread rolling action moving the tube longitudinally through thehead, and

means responsive to the thread rolling action producing longitudinalmovement of the tube to control said power means as a servomotor to feedthe tube forwardly from the first end to the second end thereof torelieve longitudinal forces on the thread forming rolls.

11. A machine as defined in claim 10, including,

means to sense the length of the rolled thread end of the tube,

means responsive to said length sensing means to open the head to forman unthreaded land on the tube,

and said power means feeding the tube forwardly during the unthreadedland portion of the tube passage through the head.

12. A machine as defined in claim 11, including,

a mandrel of a length exceeding the length of the tube to be rolled andhaving first and second ends,

and motive means to move the mandrel first end longitudinally into thefull length of the tube from the second end to the first end.

13. A machine as defined in claim 12, including,

the thread rolling action on the tube longitudinally elongating the tubeand frictionally moving the mandrel forwardly so that the first endthereof moves away from the first end of the tube,

and said motive means moving the mandrel rearwardly during movement ofthe tube for the unthreaded land portion of the tube to have the firstend of the mandrel moved adjacent the first end of the tube.

14. A thread rolling machine, comprising in combination,

a frame having first and second ends,

a carriage movable longitudinally on said frame,

a hydraulic motor connected to drive said carriage longitudinally ofsaid frame,

a hydraulic servovalve having a housing and a valve spool,

means to move said servovalve housing with movement of said carriage,

means to connect a tube to be threaded to said valve spool to move same,a mandrel longitudinally movable relative to said frame, a threadrolling head including a plurality of thread rolling rolls journalledfor free rotation thereon, motive means to move said mandrellongitudinally inside of the tube to be threaded into engagement withsaid carriage,

said rolling head being openable and being closable to engage a tube forrolling threads thereon,

means to establish a controlled feed rate of said hydraulic motor for aforward longitudinal movement of the carriage and tube,

means to rotate said roll head,

means to close said roll head to roll a thread on the exterior surfaceof the tube with the tube held against rotational movement and with themandrel preventing collapse of the tube during rolling of the thread,

the rotation of said rolling head threading itself onto the tube andpulling the tube longitudinally to move said servovalve spool in saidforward longitudinal direction,

means connecting said servovalve to said hydraulic motor for control ofsame to establish forward movement of said carriage under control ofsaid servovalve,

a tube length sensing device adjacent said mandrel and disposed nearsaid second end of said frame,

said tube length sensing device contacting the forward end of the tubeduring forward longitudinal movement thereof to be moved forwardlytherewith,

means cooperating with said tube length sensing device to open said rollhead to establish an unthreaded land on the tube,

said controlled feed rate of said hydraulic motor continuing themovement of said carriage to produce said unthreaded land,

the tube elongating during the thread rolling action and causing saidmandrel to move longitudinally away from said carriage,

and said motive means returning said mandrel into engagement with saidcarriage during the period of establishing said unthreaded land.

15. The method of using a roll head having rolls to roll a helical formon a tube, comprising the steps of,

relatively longitudinally forwardly moving the tube and the roll head bypower means at a first rate,

relatively rotating the tube and roll head and causing the rolls thereonto engage the exterior surface of the tube with the relative rotation ofthe head and tube causing relative longitudinal movement therebetween ata second rate in accordance with the rotational speed and pitch of thehelical form,

said second rate being different from said first rate,

and controlling the rate of movement of said power means in accordancewith said second rate.

16. The method as set forth in claim 15, including,

journalling the rolls for free rotation on the roll head.

17. The method as set forth in claim 15, including,

holding the tube non-rotatively and rotating the roll head,

and holding the head non-longitudinally movable and moving the tubelongitudinally through the roll head.

18. The method as set forth in claim 15, including,

inserting a mandrel in the tube,

measuring the length of the externally formed portion of the tube,

controlling the opening of the head in accordance with said measuredlength to establish an unformed land on the tube,

the form rolling action elongating the tube and thus causing the mandrelto frictionaily move longitudinally with the portion of the tube beingform rolled,

and moving the mandrel during the roll head open conditions whichestablished the unformed lands to maintain the mandrel in a positioninside the tube at the roll head.

References Cited UNITED STATES PATENTS 1,860,989 5/1932 Brinkman 72-961,982,369 11/1934 Brinkman 72 96 2,092,873 9/1937 Brinkman 72-1182,157,598 5/1939 Fentress et al 72ll2 2,669,278 2/1954 Andersen 72--1182,714,919 8/1955 Johnston 7296 2,757,706 8/1956 Johnston 72-96 3,137,9266/1964 Barlow et a1. 72-367 3,203,256 9/1965 Lehnert 72-77 3,262,295 7/1966 Wolosynek 7225 CHARLES W. LANHAM, Primary Examiner.

E. M. COMES, Assistant Examiner.

1. A FORM ROLLING MACHINE, COMPRISING IN COMBINATION, A FRAME, ACARRIAGE MOVABLE LONGITUDINALLY ON SAID FRAME, A MOTOR CONNECTED TODRIVE SAID CARRIAGE LONGITUDINALLY OF SAID FRAME, A FORM ROLL HEADINCLUDING A PLURALITY OF FORM ROLLING ROLLS THEREON, MEANS TO RELATIVELYLONGITUDINALLY MOVE SAID ROLL HEAD AND A TUBE TO BE FORM ROLLED INACCORDANCE WITH LONGITUDINAL MOVEMENT OF SAID CARRIAGE, MEANS TOESTABLISH A CONTROLLED FEED RATE OF SAID MOTOR FOR A FORWARDLONGITUDINAL MOVEMENT OF THE CARRIAGE, MEANS TO RELATIVELY ROTATE SAIDROLL HEAD AND THE TUBE TO ROLL A FORM ON THE EXTERIOR SURFACE OF THETUBE, A CONTROL ELEMENT AND HOUSING, THE RELATIVE ROTATION OF SAID ROLLHEAD AND TUBE WHILE IN ENGAGEMENT RELATIVELY LONGITUDINALLY MOVING THETUBE AND THE HEAD, MEANS TO RELATIVELY MOVE SAID CONTROL ELEMENT ANDHOUSING IN ACCORDANCE WITH RELATIVE LONGITUDINAL MOVEMENT OF SAID ROLLHEAD AND THE TUBE, MEANS CONNECTING SAID CONTROL ELEMENT AND HOUSING TOSAID MOTOR FOR CONTROL OF SAME TO ESTABLISH FORWARD MOVEMENT OF SAIDCARRIAGE, AND MEANS CONNECTING SAID CONTROL ELEMENT AND HOUSING FORRELATIVE FOLLOWUP MOVEMENT IN ACCORDANCE WITH LONGITUDINAL MOVEMENT OFSAID CARRIAGE.